Control surface boost device and gust dampener



' March 1946- E. FUB URTON EI'AL Re. 22,728

v I CONTROL SURFACE BOOST DEVI GE AND GUST DAMPE INER Original Filed Ila rah 28'. 19:59 2 Sheets-Sheet 1 I mw szvmxi;

u -law 2 Sheets-Sheet 2 r INVEN 023 March 5, 1946. E. F. BURTON ET AL CONTROL SURFACE BOOST DEVICE AND GUST DAMPENER Original Filed March 28, 1939 lmv| Ill nw hw QW Reloaded Mar. 5, 1946 CONTROL SURFACE BOOST DEVICE AND GUST DAMPENER Edward F. Burton,

Los Angeles;

Orville A.

Wheelon, Pacific Palisades, and Harold W. Adams, Santa Monica, Calif., asslgnors to Douglas Aircraft Company, Incorporated, Santa Monica, Calif.

Original No. 2,366,382, dated January 2, 1945, Se-

rial No. 264,544, March 28, 1939. Application for reissue January 30, 1945, Serial No. 575,324

. 2} Claims. (Cl. 244-'85) Our invention relates to improvements in aircraft surface. controls with particular reference to a hydro-mechanical booster mechanism for actuating the control surfaces and thereby relieving the pilot by decreasing the manual elfort necessarily expended for such actuation, particularly on large airplanes. The invention also incorporates a gust dampening feature wherein the enflaps, aerodynamically balanced surfaces, locking clamps and locking, pins are not generally satisfactory due 'to certain undesirable features. First, the hydraulic servo units which are controlled by a conventional valve provide no follow up or load feel; returning this valve to non tral merely allows a surface so controlled to main in the displaced position. Second, the automatic pilot remote control units do not oper ate from the manual controls, do not provide load I feel and do not afford a sufficiently convenient and rapid control for use during take-oil" or land;

. gine or booster prevents violent and sudden gusts from rapidly actuating and possibly damagingiii they are attached. Even the sliding pin lock, al-

though controllable from the cockpit, is often not releasable when the control surface is under load as it would be under take-off and flying conditions. Use of these locks is doubly dangerous in large airplanes where the surface is distant from the controls because even though the pilot should flex the cockpit controls as a check before takeoff, there is usually sufllcient deflection in the control cables and supporting structure to allow cockpit control movement without indicating that the surfaces proper are locked.

The principal object of the invention is to provide an aircraft surface controi system wherein the force required to move the cockpit controls a given amount oi proportionately less than the force necessary to actuate the control. surface a corresponding amount.

Other ohiects are: to provide a hydrmniecham lcal control surface hoe-steer which can be used to reduce control forces under all flight conditions; provide a hydro mechanical contr surface booster which afiords a positive coordination between cockpit control and the control sur- Lun -wto provide a hydro-mechanical control. surface booster which will transmit load feel to the cockpit controls.

log. Third, the booster flaps on the control our faces serve the general purpose of reducing the pilot's effort, but are undesirable from the stand '1 point of their tendency to decrease the natural stability of an airplane. Fourth, aerodynamically balanced surfaces have contributed greatly to control force reduction but with the ever in creasing size of aircraft, the forces have also increased to the point of becoming unwieldy and. fatiguing in operation.

Gust dampeners or locks which are generally used while an airplane is at rest consist eitherof clamps placed partially on the movable control surface and partially on the adjacent fixed surface or of a sliding pin lock arrangement releasable from the cockpit. *Bothof these methods. while they effectively prevent wind gusts from displacing the surfacesof an airplane on the ground, cannot be used while the airplane is in flight. In fact, their use on the ground presents an extremely dangerous possibility in that they may be inadvertently left in place at take-oil, thereby rendering useless the controls to which Still further objects are "to provide a hydra mechanical control surface booster which lessen the fatiguing duties of air transport pilots; to provide a hydro mechanical control surface booster wherein the ratio of force applied at the control surface to the force applied at the pit controls can be varied between a pred ct-er mined minimum and infinity; to provide Toyciro-mechanical control surface booster which can be utilized in combination with an automatic pilot; to. provide a control surface dampener which efiectively prevents sudden gusts from rapidly actuating the surfaces both on the ground and in the air; and to provide a control surface gust dampener which, while preventing sudden gusts from rapidly actuating the surfaces, permlts free controllability by the pilot.

Another object of our invention is to provide a control surface gust. dampener which operates at the surface rather than transmitting loads through the control system.

Other and further objects willbecome apparent as the description proceeds.

In the accompanying drawings:

Figure 1 is a schematic diagram showing the control surface boost and gust dampening system.

Fi ure 2 is {Sectional elevation of the control ed into the cylinder housing at I 02.

surface boost and gust dampening valve and pis-' ton unit. I

Figure. 3 is a sectional view or the hydraulic snubber unit taken on line 3-3 of Figure 1; and

Figure 4 is a view of a portion oi the linkage mechanism taken on line 4-4 of Figure 1.

A system incorporating our control surface boost and gust dampening mechanism is shown in Figure 1, the numeral l indicating an electric or hydraulic motor or other power supply which drives a pump ii having an intake port II and a pressure port It. Port i2 of the pump is connected by a line II to a fluid supply such as a reservoir ii, and port I! is connected by a line II to a valve and piston unit II.

The unit, shown in detail in Figure 2, includes a body It which houses a shuttle valve I! and a piston 20. Valve is reciprocates in a. valve chamher 2! having a plurality of ports 28-2128-' 28-", port 21 communicating with the line I8, Piston Ill reciprocates in a cylinder ll having ports 32-", port 32 communicating through a passage 34 with valve port 28, and port 33 communicating through a passage 35 with valv port 30. Valve ports 28-48 are connected by lines "-4! at 42, from which point aline 43, incorporating a snubber cylinder 80, continues to a T 44. From this T a-line 45 incorporating a pressure relief valve 48 returns to reservoir l5, and a line incorporating a check valve 41 connects into line ll.

age in the pressure tank A dash pot 48 is provided at the end of valve chamber 2!, and the portion of valve II which rides in the dash pot includes a piston head 44. Head ,4! divides the dash pot into two portions "-5 I connected to line It by a line 53. Also, the dash pot portions are interconnected by a restricted line I4 to afford a retarded from one dash pot portion to the other.

Snubber cylinder sills connected into line 48 and acts as a constant speed control of fluid flow through the system. The cylinder comprises a housing OI having a bore 92 into which a cage type sleeve 93 with openings 84 is pressed. An inlet port It is provided in thebottom of the housing and leads to bore 92. An outlet port 98 is provided in the side oi" the housing approximately intermediate the ends and connects with an annular recess 91 within the housing and concentric with the -bore 92. The sleeve is so arranged withinthe housing that its openings 94 connect with the annular recess in a transverse relation to the outlet port 86. A piston 98 is mounted in the bore 92 and has a metering ori-' flce 98 which is adapted to'create a pressure drop in the cylinder. The piston is held at the bottom of the bore by springs illli until fluid entering port 95 confronts the piston, creates pressure by reason or the metering oriflce and forces the piston upwardagainst the spring thereby closing the openings in the sleeve. The springs are retained by the piston and a cap III thread- This can also secures the sleeve in place and has three prongs ill which extend into -the annular recess and serve as a stop. for the piston. Two

small holes I04 are provided in'thesleeve Just and these holes also are above the openings 94 within the area of the annular recess; however, they are located suii'iciently high that they cannot be shut 01! by the piston as it is stopped by the prongs of the cap at the upper'end 0fthe portion 50 being connected back to line II by a line 52, and portion Ii being cans ' tween. the pump and the pressure tank; a valve assures the presence of fluid in the shuttle valve and dash pot system in the event of leakor line between valves 59 and "land fluid is further retained in the dash pot by valves tl-Gl, located respectively in lines 52-58.

The shuttle valve i8 extends at each end from housing is and is sealed against fluid leakage by packing glands 65-48. End 61 of the valve is adapted for the attachment of an operating linkage and end 68 merely moves to and from the housing as the valve reciprocates.

Piston Zll extends from the housing at one end and is sealed by a head assembly 89 incorporatmg a packing ill. At the other end. a h ll w elongated head assembly ii seal the piston and houses it throughout its travel. I

The unit I1 is supported at one end by head assembly 1| attached to a torque arm 12 which is in turn fixed to a control surface torque tube ll, and at the other end by the piston 20 pivotally connected at 14 to a threaded collar 15. The collar is adapted to move on a worm type lever 16, swingably connected to a fixed structure bracket 11, in response to rotation of the worm by an electric or hydraulic motor 18,

drive. A stationary collar 19 is provided at the upper end ct -lever 18 and afl'ords a, pivotal connection for a rod 80 extending rightwardly and The lower main arm 81 of the bellcrank is slot ted at 8B in a manner suitable to receive a pin 89, the pin being bracketed to the torque arm 12 which supports the piston head assembly 1|, and is fixed to the control surface torque tube.

The operation of our controlsuriace boost and gust dampening system will now be described:

with the system fllled with fluid, the power supply i0 driving pump ll keeps the oil circulating under pressure, the fluid being drawn from reservoir it through line l4 and expelled under pressure from pump port I 3 into line it. Check valve I! prevents fluid from returning to the pump in the event of a failure ahead of the valve. Pressure tank 58, being or the'oil and air chamber.

type with a flexiblediaphragm, as disclosed in our copending application, Serial No. 308,414, is connected. into line lt and serves to assure a constant pressure in the system and eliminate surges by absorbing them through the flexible diap I Pressure is now available in thedash pot as by reason of its connection with line It, and at the shuttle valve into which line ll directly connects.

'As the control cables 83-44 are actuated, the bellcrank "is pivoted about thecontrol surface or cable the control surface torque 9N tube 18 until one end of slot". depen ing upon the direction of motion, contacts the pin 89 attached to torque arm II. This pivotal motion of the bellcrankalso actuates the linkage ll which controls the movement of the shuttle valve.

the slot and is fully open when either end of the slot and the pin are in contact. The direction in which the valve is open depends upon the slot end with which the pin is in contact.

For example, when the pilot pulls on cable 83, the bellcrank rotates about the control surface 1 torque tube in an anti-clockwise direction. This motion displaces the shuttle valve which begins to connect pressure port 21 with passage 35 leading The mechanism is so arranged that the valve is closed when the pin is in the center of unit ll floats between the pivotal lever I8 and the torque arm 12, force is exerted on both the lever and the torque arm. The force acting on the torque arm rotates the control surface anti clockwise and the force acting on the lever moves it leftward in an arcuate path. This lever mov ing leftward also actuates the rod 80 in a leftward direction and the rod, by its connection to bellcrank 8! tries to rotate the bellcrank in a clockwise direction against the opposite force being exerted by the pilot.

It may be seen then that the piston forcing the torque arm 12 rightward in an arcuate motion and therod 80 leftward would tend to move the tained by setting the threaded collar is. to which piston II is attached, at a certain location on'theworm type lever ll. In the preferred embodiment this 5 1 location is obtained at the upper end of the threaded coilar's travel on the worm. This then is the predetermined minimum and the ratio may be increased to infinity by bringing the collar down on the worm to the lower end of the travel, which position'corresponds to the dead center location between the piston and the lever 10. n 1

Load feel is transmitted to the pilot through his necessary effort to overcome the force of rod 80 i as previously described, this effort being a submultiple or one-fifth the load present at the surface.

Returning now to the displacement-oi piston 20: As the pressure enters through passage 35, the fluid present on the other side of the piston is forced out through passage 34, through the valve chamber and into return line 40 via port 28. Line 40 connects with return line 43 which incorporates the snubber cylinder 90. The oriflce 89 in the spring loaded piston 98 of this snubber retards the return flow of V fluid which causes pressure to build up until the spring is compressed.

Piston 98 then rises until it strikes a stop, at which location it closes the outlet port in the snubber halting all but the slightest flow of return fluid. Halting the flow in this manner causes pressure to build up in the exhausting side of the piston 20 and consequently slows-down the operation of the system. with the snubber piston in the uppermost end of its travel, the fluid flows through the orifice 99 until pressure plus the power of the spring is sufiicient to return the piston downward, opening the ports in the sleeve slot and pin relative to each other in opposite directions until the pin is centered in the slot and the'valve closed, whereupon the pressure is shut of! and the piston halted.

The efforts required of the pilot then must be sufficient to overcome the force being exerted through the rod an, which would be the power required to prevent the pin from moving to the center of the slot as the piston moves the torque arm rightward. In other words, the pilot must resist the force of the rod 80 and keep the slot in the same relation to the pin as it was when he first pulled on the cable and opened the valve, otherwise, the piston moving the torque arm, to which the pin is attached, will close the valve and stop the pressure movement,

The pilot is able to resist the force of rod Bil due to the leverage relation of the connections between the bellcrank and the rod 80, the rod 80 and the pivotal lever 18, and the pivotal lever 18 and the piston 20. This leverage is such that the force exerted by the pilot is a sub-multiple of the force required to operate the surface. Otherwise stated, the pilot constantly pullin on the control cable is constantly moving the slot so that 93 so that fluid can continue its return flow through line 43 and back to the reservoir. In the event anything happens such as spring breakage, etc., to prevent the snubber pistonreturning from its shut off position, small holes I04 are provided in the sleeve just above the large openings 94. These small holes are located high enough to prevent their being closed by the piston, so they will always allow a. small amount of fluid to exit through port 96 in the snubber cylinder.

the pin is off-center. and the piston is constantly trying to center the pin thereby moving the control surface. The-force exerted by the pilot is multiplied at, for instance, a ratio of 5 1 so that when he moves his controls ten inches with a force of twenty pounds, the piston and linkage will move the control surface ten inches with a force of one hundred pounds. If only a ten pound force is required to move. the control surface, only a two pound exertion will be required of the pilot.

The present preferred ratio between the force required to move the control surface and the force applied by the pilotis 5 z 1 and this ratio-is ch- This snubber is in effect a governor controlling the speed with which the boost system can be operated and, while itpermits operation rapidly enough from a standpoint of controlling the surface, 'it prevents wind gusts from suddenly actuating the surface thereby possibly causing damage.

The operation of the system as described thus far has been with respect to the pilot exerting force on cable 83 to obtainan anti-clockwise ously described. Also the relative movement of the pin and the slot is the same except that the opposite end of the slot is brought into contact with the pin, and the valve is moved in the leftward direction. This connects pressure port It with passage 34 and the fluid forces the piston rightward thereby pulling the control surface torque arm 12 and the pivotal lever ll towards one another. -This is possible because the piston rod is allowed to move into the hollow elongated head assembly ll of the valve and piston unit H. The lever and rod linkageoperates to obtain the same result as heretofore except from :1 to infinity. I

The means for gust dampening is also eil'ectivethat the rod III is now pushing against the pilot instead of pulling.

The snubbe'r operation for each movement is identical as both return lines ill-4i are teed into the snubber cylinder.

An important feature of the invention is that when the member 15, Figure 1, which is connected to the lever 12 of the airfoil through the motor or power means i1, is moved a short dis tance by thepilot, the power means II operates to add a supplementary movement to the movement of the part 15 so that the displacement of the lower end of the lever 12 includes the small movement of the part 15 and the larger supplementary movement of the cylinder and extension II of the power-means II. For example, if the part 15 is moved to the right a distance D, the power means II will be actuated so as to shift the body I! and the extension ll rightward relatively to the piston through a distance nD. Since the piston 20 is directly connected to the part 'l, the rightward movement of the part II will move the piston 20 rightward, and to this movement of the piston 20 will be added the suppbmentary movement of the body It and the extension H in rightward direction so that the member II will move the lower end ofthe lever 12 through a distance which is the summation of the movements of the part 15 and of the body ll,v or D+nD. Disregarding friction, whatever force the pilot or operator must apply in order to move the member it depends upon the reaction of the airfoil against movement exerted through the lever II. It will be perceived that through the linkages described, the reaction of the airfoil and wind loads thereon is constantly transmitted. back to the pilot, and that whenever he transmits to the airfoil a small movement through movement of the member 15, the power means I! will act to add to this small movement a larger supplementary movement without interfering with the load feel which is carried" back through the linkages to the hand of-the pilot.

The-gust dampening feature oftheinvention, in addition to the snubber cylinder action, operates on the reduced load principle andit may be readily seen that sudden gusts will have little effect upon the pilot's control in flight by the time the gust power hasbeen divided by five;-

The sudden action is still further damped by the shuttle valve dash pot ll which" exerts a drag or snubbing effect on the valve movement. When the airplane is to be parked on the ground.

the effectiveness of the dampening action can be 1 enhanced by moving the threaded collar I5 to the lower end of its travel which increases the ratio between the surface and the pilot's control during the time the hydrauli system is for any reason inoperative. For example, should the pressure supply in the hydraulic system be discontinued, as for example by stopping of the pump l l or rupture of piping M or the reservoir II. the

check valve III will prevent a reserve flowupward from the cross-fitting to which check valve 60 is connected andloss of fluid from the flexibleconduit 48 into the rigid conduit leading to the reservoir II will be prevented by the pressure release valve 48 which may be set so that fluid will not pass therethrough until a reasonable pressure, for example, ten or twenty pounds, is applied to the v fluid, The movement of the fulcrum lever 82,

under this condition, will be transmitted directly through the pin II to the lever 11, thereby directly moving the airfoil. Movement of the ful- I in its present preferred embodiment, it will be crum lever "will betransmitted through the link 80 to the lever 16, with the result that there will 'be an elongation .andcontraction of the hydraulic device H as the fulcrum lever 82 isrotated respectively in counterclockwise and clockwise di. rection. The resultant movement of the piston 20 .in the cylindrical body i8 will result in a'move merit -of hydraulic fluid outward through either pipe 40 or 4|, depending upon the direction of movement of the piston 20. In view of the fact that the outward flow of fluid through either pipe 40 or 4| must pass through the snubber cylinder 80, such discharge flowof fluid is constantly vunder the control of the snubbing device incorporated in the cylinder 90, and therefore the movement of the piston 20 within its cylinderis at all times limited, with the result that the hydraulic unit H at all times controls the velocity of movement of the fulcrum lever 82 and of the airfoil, V and even though the pilot were applying no force to the fulcrum 82, an external force applied to the airfoil can not throw the airfoil and the operating parts connected'thereto abruptly into'one extreme position or the other. An im ortant feature of the present invention is the dual control of the airfoil, providing a highly desirable safety factor. The pin 89 is constantly positioned within the slot 88 of the lever 82, so that in the event of failure of the hydraulic system movement of the airfoil maybe accomplished by the direct connection of the fulcrum lever ii! through the pin 85 with the lever 12 associated with the airfoil.

The preferred embodiment operates under 800 pounds per square inch pressure but this of course may be varied to suit the particula: installation requirement.

While we have described our invention in detail obvious to those skilled in the art, after-understanding the invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. We aim in the appended claims to cover all such modlfications and changes.

We claim:

-1. In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and 0' 5 and transmitting load feel to the said manual means, the second said means comprising a pivo linkage means for multiplying the manual energy I tal lever spaced from said movable airfoil and a hydraulic valve and piston unit floatingly suspendedtherebetween, a linkage connecting said manual means with the valve and a rod connecting said manual mean with said pivotal lever,

whereby operation of said manual means reciprocates the said valve thereby directing pressure fluid to the said piston which is displaced and transmits force both to the airfoil and the pivotal lever, the force to the airfoil rotating same and.

the force to the lever transmitting load feel to the manual means in a sub-multiple of the load required to actuate the said airfoil 2. In an airplane control system including a movable airfoil, manually operable mean for controlling the said airfoil, and hydraulic and linkage means'for multiplying the energy exerted by the said manual means,-the second-said means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve and piston unit I suspended therebetween, "a' linkage connecting said manual means, the valve and the pivotal lever wherebyoperation of said manual means reciproto the said linkage, the arrangement of the said the force transmitted thereto is a sub-multiple of the force rotating the linkage being such that airfoil.

3.0!n a'n airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the manual energy and transmitting load feel to the said manual means, the second said means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve and piston unit floatingly supported therebetween, a linkage connecting said manual means with the valve and a rod conmeeting said manual means with said pivotal lever, said lever being so organized and arranged that the position of the said valve and piston unit may be changed with relation to the position of the rod thereby varying the multiple of the energy exerted by the hydraulic and linkage means relative to theenergy exerted by the manual means.

4. In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the energy exerted by the said manual means, the second said'means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve and piston unit floatingly suspended therebetween, a linkage connecting said manual means, the valve, and the pivotal lever whereby operation of said manual means reeiprocates the said valve thereby directing pressure fluid to the said piston which is 6. In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the manual energy and for governing the speed of control, the second said means comprising a pivotal lever spaced. from said movable airfoil and a hydraulic valve, 1

piston, and snubber unit floatingly suspended therebetween, a linkage connecting said manual means with the valve and a rod connecting said manual means with said pivotal lever, whereby operation of said manual means reciprocates the said valve, thereby directing fluid pressure from a fluid supply to the said piston which is displaced and transmits. force to the airfoil consequently rotating same, the speed of such rotation being governed by the passage of fluid from the piston as same is displaced, said fluid flowing through the said snubber wherein the flow is restricted to a predetermined rate thereby precludingoperation of the airfoil at a speed in excess of said rate either by the manual control means or by external forces acting on the airfoil.

7. In an airplane control system including a movable airfoil, manually operable means'ior controlling the said airfoil, and hydraulic and linkage means for multiplying the energy exerted by the said manual means, the second said means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve and piston unit suspended therebetween, a linkage connecting said manual means, the valve and the pivotal lever whereby operation of said manual means reciprocates the said valve thereby directing pressure fluid from a fluid supply to the said piston which is displaced and transmits force both to displaced and transmits force both to the airfoil and the pivotal lever, the force to the airfoil rotating same and the force to the pivotal lever being transmitted to the said linkage, the arrangement of the linkage being such that the force transmitted thereto is a sub-multiple of the force rotating the airfoil, and means for adjusting one portion of the linkage relative to another portion whereby-the multiple of the force may be varied.

5. In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the manual energy and for governing the speed of control, the second said means comprising a pivotal'lever spaced from said movable airfoil and a hydraulic valve,

piston, and snubber unit floatingly suspended therebetween, a linkage connecting said manual means with the valve and a rod connecting said manual means with said pivotal lever, whereby operation of said manual means reciprocatesthe said valve, thereby directing fluid pressure from a fluid supply to the said piston whichis displaced and transmits force to the airfoil consethereby precluding operation of the airfoil at a speed in excess of said rate by any external means or forces.

theairfoil and the pivotal lever, the force to the airfoil rotating same and the force to the lever being transmitted through the linkage to the manual control means, the linkage being so organized and arranged that the force transmitted therethrough is a sub-multiple of the force rotating said airfoil, the multiple ratio between the two forces being variable by changing the arrangement of the linkage means with respect to the pivotal lever and the hydraulic piston.

8. In an airplane control system including a movable airfoil, manually operable means for controlling the said airfoil, and hydraulic and linkage means for multiplying the manual energy and for governing the speed of control, the second said means comprising a pivotal lever spaced from said movable airfoil and a hydraulic valve, piston and snubber, the piston being floatingly suspended betweensaid lever and said airfoil, a linkage connecting said manual means with the valve and piston and a rod connecting said manual means with said pivotal lever, whereby operation of said manual means reciprocates the said valve, thereby directing fiuid pressure froma fluid supply to the said piston which is displaced and transmits force both to the airfoil and the pivotal leverwthe force to the airfoil rotating same and the force to the lever being transmitted therethrough to the rod connected to the manual control means, the rod and linkage being so arranged that the force transmitted to the airfoil is a multiple of the force transmitted through the manual control means, the multiple ratio between the two forces being variable by changing the position of the rod with respect to the pivotal lever and the hydraulic piston, and the speed of operation of the airfoil being governed by 'the passage of fluid from the .piston as same is displaced, said fluid flowing stricted to a predetermined rate thereby precluding operation of the airfoil at a speed in excess of said rate by any external means or forces.

9. In an airplane control system, a movable airfoil and a gust dampening means for said airfoil, said means comprising a hydraulic piston havingcontrol means actuatable by excess force applied to said piston to limit the movemeni it hereof, and linkage mechanism both of which are connected to said airfoil in' a manner such" that forces resulting fromwind gusts acting on said airfoil actuate said control means are snubbed by said hydraulic piston and reduced in energy by said linkage-mechanism, the amount of energy reduction being variable from a pre- ,lic piston and linkage actuated by the first said means to multiply the manual energy, and an adjustable lever cooperative with the said piston and linkage to vary the multiple.

11. In a power control for an airfoil, the combination of: pilot operated control means having a part movable throughconsecutive positions airfoil and transmitting said force to said airfoil which is a, fraction of the movement of said pilot operated member and with a force which is a multipleof the force applied to said pilot operated member; and means connecting said part of said mechanism to said operating member of said operating member, said last named means includwithin a prescribed range; a member connected to the airfoil whereby movement may be transmitted to the airfoil, said member being positioned so as to have movement relative to said movable part of said control means; power'means for moving said member'whereby movement of said airfoil is accomplished; a control element for said power means connected to said part and to said member so that movement of said part relative to said memberwili actuate said control element to effectuateoperation of said power means which will move said member in a direction to follow the movement which has been imparted to said part; and means disposed in series with said power means operating automatically to transmit to said control means a reaction proportionate to the force transmitted at any time through said member to move said airfoil.

12. In a power control fo an airfoil, the combination of: pilot operated 'control means movable through selected arcs of movement within a (prescribed range of movement; a motor operated in consequence of the movement of said control means to move said airfoil, said motor having a movable active part connected to said airfoil and a movable reactive part; and a linkage mechaing a motor arranged to multiply the movement of said part of said mechanism and transmit to said airfoil operating member a multiple of the movement of said part.

15. In a power control for an airfoil, the com-. bination of: an operating member connected to said airfoil whereby the same may be moved; a pilot operated member mounted for operative movement; force multiplying means connected to said pilot operated member, having a part moving in accordance with the movement of saidpilot operated member, through a distance which is a fraction of the movement of said pilot operated member'and with a force which is a multiple of the force applied to said pilot operated member; and a power strut connecting said part to said operating member .of said airfoil, said power strut having means operating to automatically change the length thereof as said part moves so that the movement trans? mitted by raid power strut to said operating memher will be a multiple of the movement of said part and proportionate to the movement of said pilot operated member.

16. In a power control for a movable airfoil, the combination of: an operating member connected to said airfoil whereby the same may be moved; a pilot controlled member mounted for operative movement; a force multiplying lever linked to said pilot controlled member and having a part moving in response to movement of said pilot controlled member, through a distance which is a fraction of the movement-of said pilot controlled member and with a force which is a multiple of the force applied to said pilot controlled member, and'means connecting said part of said lever to said airfoil operating member nism connecting said reactive part'of said motor 1 to said control means whereby the force and extent'of the reactive movement of said motor will be transmitted to said controlmeans.

13. In a power control for an airfoil. th combination of: pilot operated control means movable through selected arcs of movement within a prescribed range of movement; a motor operated in consequence of the movement of said control means to move said airfoil, said motor having a movable active part connectedto said airfoil and a movable reactive part; and link means connecting said reactive part of said motor to said control means whereby a fraction of-the force and extent of th reactive movement of said motor will. be transmitted to said control means.

14. In a power control for an airfoil, the combination of: an operating member connected to said airfoil, whereby the same may be moved; a

and transmitting said force thereto, said last named means including a motor arranged to multiply the extent of movement of said part of said lever and to transmit to'said airfoil operating member a multiple of the movement of said part.

1'7. In a control of the character described whereby amember may be moved by power without sacrificing sense of load-feeLon the part of the operator, the combination of: a part moved by the operator; meansconnecting said part to said member so that movement of said part produces a movement of said member; power means connected to'said member so as to impart to said member, in-addition to said movement, a supplementary movement so that the displacement of said member will include the movement of said part "and said supplementary movement; and means to correlate the operation of said power means with the movement of said part.

18. In a control of the character described whereby a member may be moved by power withoutsacriticin'g sense ofload-feel on the part of pilot operated member mounted for operative movement: a force multiplying mechanism connected to said pilot operated member andhaving connected to said member so as to impart to said the operator, the combination of: a part moved by the operator; means connecting said part to I said member so that movement of said part produces amo'vementfof said member; power means member, in addition to said movement, a supplesauna mentary movement so that the displacemmt of said member will include the movement of said part and said supplementary movement; means to correlate the operation of said power means with the movement of said part; and a lost mo-' .member; a movable airfoil: a train of power transmitting devices between said member and airfoil for delivering the manual energy of the pilot to the airfoil to move it, including two devices having a lost-motion power transmittingconnect-ion therebetween; a second train of power transmitting devices between said two devices including a hydraulic strut arranged when energizcd to power multiply the manual force delivcred thereto. said second train being also arranged to deliver the manual energy of the pilot to the airfoil to move it in the same'sense as said first train; and a valve for the two way energization of said strut and movable from neutral for said energizations in response to movement or said lost motion connection from a midway position toward its two extreme positions respecthe air loads upon the surface reach equilibrium with the force then developed by the power means, control means movable to vary the force developed by said power means, pilot operable means operabl to move said control means. and

resisting means operable to resist operation of for subjection to the air reaction thereon. but in lesser degree, to increase such resistance to operation of said control means in correspondence with, but lesser in amount than. the increase in air loading upon the control surface, up to the limit of the force of the power means, or of the pilot to move the control means.

21. In combination with a swlngable aircraft control surface, torque means carried by the.

control surface to swing it in opposition to air loads acting upon it, hydraulic Jack means operatively connected to actuate said torque means,

amast plvotally mounted upon the control Surface for swinging under the control of the pilot relative to said torquemeans, and lack control means operatively connected to said mast and to said jack means. operable by swinging of said mast relative to said torque means to actuate said jack means for moving said torque means in a direction tending to return said mast and said torque means to their initial relationship while simultaneously swinging the control surface.

22. In combination with an aircraft control surface, such as a rudder, movable from a position of minimum air loads through successive positions of increased air loads resisting such departure, a jack connected to the rudder so to move it. and control means interposed between said pilot operable means by the pilot to move a said control means for increasing the forcedeveloped by the power means, and hence to effect further movement of the control surface to a position of greater air loads. said resisting means being operativeiy connected-to said power means the jack and a fluid pressure source comprising a valve assembly including a normally closed valve, manually operable means engaging the valve to open the same for admission of pressure to the jack, and means operable in response to pressure so admitted to the lack and thereby directly related to the reaction on said lack of the airloads upon the rudder in its position of departure, and operatively associated with the valve to resist opening movement thereof and to impose a variable resistance upon'the manually operable means which is a factor of the total air load upon the rudder. and is equal to the force applied to said manually operable means.

snwsnn r'. BURTON. onvmn s. HAROLD w. spans. 

